Bug 836822.  Convert MathML elements to WebIDL.  r=peterv
Bug 830992 part 1.  Make it possible to pass CallbackObject& as the thisObj for callback functions.  r=peterv
Bug 830992 part 2.  Switch DOMTransaction to WebIDL codegen.  r=wchen,peterv
Bug 836920.  Move dom::Optional<> and dom::Sequence to BindingDeclarations.h so using dictionaries in interfaces whose name comes before 'PrimitiveConversions' alphabetically does not break. r=peterv

All the code is just moving except the Optional<nsAString>::operator=
that takes a FakeDependentString.  That had to be changed so it has no
dependency on the actual definition of FakeDependentString.